Post on 09-Mar-2021
DLR’s Contribution to the Helmholtz Virtual Institute Solar Syngas: Materials for solar-thermochemical fuelsproductionStefan Brendelberger, Josua Vieten, Nicole Knobloch, Sebastian Richter, Johannes Grobbel, Brendan Bulfin, Martin Roeb, Christian Sattler
International Workshop on Solar ThermochemistryJülich, Germany 13.09.2017
Overview
- Material characterization- Thermodynamic properties- Thermal expansion- Degradation
- Material development- Tailored perovskites
- Meso scale particle production- Drip casting
- Particle characterization- Heat transfer in particle bed at high T low p
www.DLR.de • Slide 2 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
Ceria and Ceria Zirkonia: Statistical Thermodynamics
www.DLR.de • Slide 3 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
100µm
Material:Ce0.85Zr0.15O2(porous granules)
Vacancy concentration δ, the oxygen partial pressure pO2 and the temperature profile for a typical TGA experiment
B. Bulfin
Ceria and Ceria Zirkonia: Statistical Thermodynamics – Thermodynamic Model
www.DLR.de • Slide 4 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
B. Bulfin et al. Phys. Chem. Chem. Phys., 2016,18, 23147-23154
δ p O , Tδ ∙ ∙ p O ∙ exp ∆
1 ∙ p O ∙ exp ∆
0,000
0,010
0,020
0,030
1E-5 1E-4 1E-3 1E-2 1E-1
Red
uctio
nex
tentδ
p(O2) [bar]
1286°C
1237°C
1189°C
δmax ARed/AOx n ∆E R2
[barn] - [kJ/mol]
■ CeO2 0,5 12575 ±7550
0,2320 ±0,0079
206,7 ±8,2 0,9754
■ CeZr-S16
0,425 101 ± 11 0,2084 ±0,0019
121,6 ±1,4 0,9893
B. Bulfin
Redox tests of SrMnxFe1-xO3- in a thermobalance
12 °
Δ ° Δs°
www.DLR.de • Slide 5 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
Bulfin, B. et al. (2017). "Applications and Limitations of Two Step Metal Oxide Thermochemical Redox Cycles; A Review." Journal of Materials Chemistry A
B. Bulfin
www.DLR.de • Slide 6 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
oxyg
en lo
ss
..
Ce4+97pm
Ce3+114,3pm
polycrystallinesample rod
oxidized reduced
∆
Length variation:
Investigation of reduction by dilatometry[Thermal expansion]
[ Thermal expansion ] + [ (ΔV)↓ (oxygen vacancies) < (ΔV)↑ (Ce4+ →Ce3+) ]
reduction temperature
N. Knoblauch et.al., Solid state ionics,2017, 301, 43-52
N. Knoblauch
www.DLR.de • Slide 7 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
Thermal and chemical Expansion during reductionunder reduced atmosphere (pO2 = 2-7x10-9 atm )
Chemical expansion during isothermal segment
0 50 100 150 200 250 300-0,05
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0,40
leng
th v
aria
tion
[%]
t [min]
1538 K 1588 K 1641 K
0 50 100 150 200 250 3000,00
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,10
1538 K 1588 K 1641 K
t [min]
200 400 600 800 1000 1200 1400 16008
9
10
11
12
13
14
15
16
this work Körner et al. Stecuura et al. Sata et al.
x
10-6 [1
/K]
temperature [K]
→ 2
Thermal expansion coefficient
Calculated nonstoichiometric value out of the chemical expansion by a given linear relationship
Temperatur [K]
N. Knoblauch et.al., Solid state ionics, 2017, 301, 43-52
N. Knoblauch
Degradation of (Ce,Zr)O2 Redox Ceramics by selective sublimation
In a previous study on redox characteristics of ceria data suggest sublimation of ceria at high temperature above 1660K and low pO2 (2–7×10−9 atm) [Knoblauch, N.; Simon, H.; Schmücker, M., Solid State Ionics
2017,301, 43–52, DOI10.1016/j.ssi.2017.01.003].
N. Knoblauch et.al., Inorganics, Special Issue "Cerium-based Materials for Energy Conversion“ coming soon
www.DLR.de • Slide 8 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017N. Knoblauch
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
0,01
0,1
1
2,5x
10-4
3,0x
10-4
3,5x
10-4
4,0x
10-4
4,5x
10-4
5,0x
10-4
5,5x
10-4
6,0x
10-4
6,5x
10-4
CeO2 MgO ZrO2 La2O3
Vap
or p
ress
ure
[atm
]
1/T [1/°C]
Characterisation by SEMe.g. reduced Ce0.85Zr0.15O2 (1683K (pO2=2,96E-9 atm)
cross section top viewspongy surface zone
time [h] length [µm]1 2,5 2,992 5 3,873 15 6,44
Measured length of spongy surface zone after reduction at 1683K for various length of time
0 2 4 6 8 10 12 14 160
1
2
3
4
5
6
7
subl
imat
ion
zone
[µm
]
time [h]
N. Knoblauch et.al., Inorganics, Special Issue "Cerium-based Materials for Energy Conversion“ coming soon
www.DLR.de • Slide 9 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017N. Knoblauch
Characterisation by EDX and x-ray diffractione.g. reduced Ce0.85Zr0.15O2 (1683K (pO2=2,96E-9 atm)
bulk
surface
Ce0.82Zr0.18O1.89
Ce0.47Zr0.53O1.83
Ce2Zr2O7 Pyrochlore formation at the surface!
-1 0 1 2 3 4 5 6 715
20
25
30
35
40
45
50
55
Zr Ce
depth [µm]
Zr [a
t%]
45
50
55
60
65
70
75
80
85
Ce
[at%
]bulksurface
N. Knoblauch et.al., Inorganics, Special Issue "Cerium-based Materials for Energy Conversion“ coming soon
www.DLR.de • Slide 10 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017N. Knoblauch
Development of new materialsPerovskites for redox cycles
A2+M3+/4+O3-δ
∆HTiMnFeCoCu
Water splitting
CO2 splitting
Air separation
Oxygen pumps
A2+M3+/4+O3: Reaction enthalpy mainly goverenedby choice of transition metal M3+/4+
0 100 200 500 kJ/mol O
Bulfin, B. et al. (2017). "Applications and Limitations of Two Step Metal Oxide Thermochemical Redox Cycles; A Review." Journal of Materials Chemistry A
Reduction from perovskite to brownmillerite:4AMO 4AMO . O
gradual reduction possible -> non-stoichiometry δ
Image: Eames et al.
www.DLR.de • Slide 11 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017J. Vieten
Tailored thermodynamic propertiesMn-Fe solid solutions*in the fully oxidized state
SryCa(1-y)MnxFe(1-x)O3-δ
∆HTiMnFeCoCu
Water splitting
CO2 splitting
Air separation
Oxygen pumps
0 100 200 500 kJ/mol O
∆H per mol O
same crystal structure in oxidized state
Materials suitable for oxygen pumping, selection according to operation parameters
Vieten, J. et al. (2016). "Perovskite oxides for application in thermochemical air separation and oxygen storage." Journal of Materials Chemistry A 4(35): 13652-13659.Vieten et al. (2017), Redox thermodynamics and phase composition in the system SrFeO3 − δ — SrMnO3 − δ. Solid State Ionics, 308, 149-155
www.DLR.de • Slide 12 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017J. Vieten
Selection of redox material
- Low reduction temperatures1
- Non-stoichiometric redox characteristics
- Scalable synthesis
Tassel, Kageyama 2011: Square planar coordinate iron oxides
1Vieten et al. 2016, J. Mater. Chem. A
Strontium Iron OxideSrFeO3-δ
www.DLR.de • Slide 13 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017S. Richter
- High temperature solid statereaction
- Precursors: SrCO3 & Fe3O4
- Mesoscale synthesis
- Manual pestling of annealedmaterial
- Ball milling
SrFeO3-δ synthesis
www.DLR.de • Slide 14 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017S. Richter
- Drip casting
- Slurry dripped intocooled oil bath
- Separation from oil
Granulation
www.DLR.de • Slide 15 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017S. Richter
- Washing
- Drying
- Sintering
Granulation – post treatment
www.DLR.de • Slide 16 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017S. Richter
Heat transfer properties of Ceria particles at low pressures
2 cm
Thermocouples
483 kW/m²
1200 °C ceria particles 212-500 µm
p=25 Pa – 1 atm
J. Grobbelwww.DLR.de • Slide 17 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
Fixed Bed Experiment with Ceria
Investigate effective conductivity as function of temperature and pressurekbed (p,T)
Comparison with Simulation
• Simulation withcontinuum model [1,2]
• Very low heat transfer particle mixing required
• How to model a moving bed?[1] P. Zehner and E. U. Schlünder, Chemie Ingenieur Technik, vol. 44, pp. 1303-1308, 1972.[2] R. Bauer, Düsseldorf: VDI-Verl., 1977.
,
J. Grobbelwww.DLR.de • Slide 18 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
Grobbel et al., Solar Energy, coming soon
Summary- Thermodynamic data from TGA measurements- Reduction extent from dilatometry experiments- Degradation by selective sublimation- Tailored perovskites for oxygen pumping- Production of spherical Strontium Iron Oxide particles- Pressure dependence of effective thermal conductivity in particle bed
- Other topics of DLR within SolarSynGas- Indirect particle based concept- Particle-particle heat exchanger- Indirect particle reactor- Sweep gas demand- Vacuum pumping requirements- Thermo-chemical pumping- Air separation- …
www.DLR.de • Slide 19 > International Workshop on Solar Thermochemistry > Brendelberger et al. • SolarSynGas > 13.9.2017
DLR.de • Chart 20
Thank you very much for your attention!
Our work was co-funded by the Initiative and Networking Fundof the Helmholtz Association of German Research Centres, by the Federal State of Northrhine-Westfalia, by the European Commission, by the FCH-JU and by the US DOE (via subcontract).